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A lightweight,high performance expression evaluator for java
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/***
 * ASM: a very small and fast Java bytecode manipulation framework Copyright (c) 2000-2011 INRIA,
 * France Telecom All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met: 1. Redistributions of source code must retain the
 * above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions
 * in binary form must reproduce the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its contributors may be used to
 * endorse or promote products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.googlecode.aviator.asm;

/**
 * A constant pool item. Constant pool items can be created with the 'newXXX' methods in the
 * {@link ClassWriter} class.
 *
 * @author Eric Bruneton
 */
final class Item {

  /**
   * Index of this item in the constant pool.
   */
  int index;

  /**
   * Type of this constant pool item. A single class is used to represent all constant pool item
   * types, in order to minimize the bytecode size of this package. The value of this field is one
   * of {@link ClassWriter#INT}, {@link ClassWriter#LONG}, {@link ClassWriter#FLOAT},
   * {@link ClassWriter#DOUBLE}, {@link ClassWriter#UTF8}, {@link ClassWriter#STR},
   * {@link ClassWriter#CLASS}, {@link ClassWriter#NAME_TYPE}, {@link ClassWriter#FIELD},
   * {@link ClassWriter#METH}, {@link ClassWriter#IMETH}, {@link ClassWriter#MTYPE},
   * {@link ClassWriter#INDY}.
   *
   * MethodHandle constant 9 variations are stored using a range of 9 values from
   * {@link ClassWriter#HANDLE_BASE} + 1 to {@link ClassWriter#HANDLE_BASE} + 9.
   *
   * Special Item types are used for Items that are stored in the ClassWriter
   * {@link ClassWriter#typeTable}, instead of the constant pool, in order to avoid clashes with
   * normal constant pool items in the ClassWriter constant pool's hash table. These special item
   * types are {@link ClassWriter#TYPE_NORMAL}, {@link ClassWriter#TYPE_UNINIT} and
   * {@link ClassWriter#TYPE_MERGED}.
   */
  int type;

  /**
   * Value of this item, for an integer item.
   */
  int intVal;

  /**
   * Value of this item, for a long item.
   */
  long longVal;

  /**
   * First part of the value of this item, for items that do not hold a primitive value.
   */
  String strVal1;

  /**
   * Second part of the value of this item, for items that do not hold a primitive value.
   */
  String strVal2;

  /**
   * Third part of the value of this item, for items that do not hold a primitive value.
   */
  String strVal3;

  /**
   * The hash code value of this constant pool item.
   */
  int hashCode;

  /**
   * Link to another constant pool item, used for collision lists in the constant pool's hash table.
   */
  Item next;

  /**
   * Constructs an uninitialized {@link Item}.
   */
  Item() {}

  /**
   * Constructs an uninitialized {@link Item} for constant pool element at given position.
   *
   * @param index index of the item to be constructed.
   */
  Item(final int index) {
    this.index = index;
  }

  /**
   * Constructs a copy of the given item.
   *
   * @param index index of the item to be constructed.
   * @param i the item that must be copied into the item to be constructed.
   */
  Item(final int index, final Item i) {
    this.index = index;
    type = i.type;
    intVal = i.intVal;
    longVal = i.longVal;
    strVal1 = i.strVal1;
    strVal2 = i.strVal2;
    strVal3 = i.strVal3;
    hashCode = i.hashCode;
  }

  /**
   * Sets this item to an integer item.
   *
   * @param intVal the value of this item.
   */
  void set(final int intVal) {
    this.type = ClassWriter.INT;
    this.intVal = intVal;
    this.hashCode = 0x7FFFFFFF & (type + intVal);
  }

  /**
   * Sets this item to a long item.
   *
   * @param longVal the value of this item.
   */
  void set(final long longVal) {
    this.type = ClassWriter.LONG;
    this.longVal = longVal;
    this.hashCode = 0x7FFFFFFF & (type + (int) longVal);
  }

  /**
   * Sets this item to a float item.
   *
   * @param floatVal the value of this item.
   */
  void set(final float floatVal) {
    this.type = ClassWriter.FLOAT;
    this.intVal = Float.floatToRawIntBits(floatVal);
    this.hashCode = 0x7FFFFFFF & (type + (int) floatVal);
  }

  /**
   * Sets this item to a double item.
   *
   * @param doubleVal the value of this item.
   */
  void set(final double doubleVal) {
    this.type = ClassWriter.DOUBLE;
    this.longVal = Double.doubleToRawLongBits(doubleVal);
    this.hashCode = 0x7FFFFFFF & (type + (int) doubleVal);
  }

  /**
   * Sets this item to an item that do not hold a primitive value.
   *
   * @param type the type of this item.
   * @param strVal1 first part of the value of this item.
   * @param strVal2 second part of the value of this item.
   * @param strVal3 third part of the value of this item.
   */
  void set(final int type, final String strVal1, final String strVal2, final String strVal3) {
    this.type = type;
    this.strVal1 = strVal1;
    this.strVal2 = strVal2;
    this.strVal3 = strVal3;
    switch (type) {
      case ClassWriter.UTF8:
      case ClassWriter.STR:
      case ClassWriter.CLASS:
      case ClassWriter.MTYPE:
      case ClassWriter.TYPE_NORMAL:
        hashCode = 0x7FFFFFFF & (type + strVal1.hashCode());
        return;
      case ClassWriter.NAME_TYPE: {
        hashCode = 0x7FFFFFFF & (type + strVal1.hashCode() * strVal2.hashCode());
        return;
      }
      // ClassWriter.FIELD:
      // ClassWriter.METH:
      // ClassWriter.IMETH:
      // ClassWriter.HANDLE_BASE + 1..9
      default:
        hashCode =
            0x7FFFFFFF & (type + strVal1.hashCode() * strVal2.hashCode() * strVal3.hashCode());
    }
  }

  /**
   * Sets the item to an InvokeDynamic item.
   *
   * @param name invokedynamic's name.
   * @param desc invokedynamic's desc.
   * @param bsmIndex zero based index into the class attribute BootrapMethods.
   */
  void set(String name, String desc, int bsmIndex) {
    this.type = ClassWriter.INDY;
    this.longVal = bsmIndex;
    this.strVal1 = name;
    this.strVal2 = desc;
    this.hashCode =
        0x7FFFFFFF & (ClassWriter.INDY + bsmIndex * strVal1.hashCode() * strVal2.hashCode());
  }

  /**
   * Sets the item to a BootstrapMethod item.
   *
   * @param position position in byte in the class attribute BootrapMethods.
   * @param hashCode hashcode of the item. This hashcode is processed from the hashcode of the
   *        bootstrap method and the hashcode of all bootstrap arguments.
   */
  void set(int position, int hashCode) {
    this.type = ClassWriter.BSM;
    this.intVal = position;
    this.hashCode = hashCode;
  }

  /**
   * Indicates if the given item is equal to this one. This method assumes that the two items
   * have the same {@link #type}.
   *
   * @param i the item to be compared to this one. Both items must have the same {@link #type}.
   * @return true if the given item if equal to this one, false otherwise.
   */
  boolean isEqualTo(final Item i) {
    switch (type) {
      case ClassWriter.UTF8:
      case ClassWriter.STR:
      case ClassWriter.CLASS:
      case ClassWriter.MTYPE:
      case ClassWriter.TYPE_NORMAL:
        return i.strVal1.equals(strVal1);
      case ClassWriter.TYPE_MERGED:
      case ClassWriter.LONG:
      case ClassWriter.DOUBLE:
        return i.longVal == longVal;
      case ClassWriter.INT:
      case ClassWriter.FLOAT:
        return i.intVal == intVal;
      case ClassWriter.TYPE_UNINIT:
        return i.intVal == intVal && i.strVal1.equals(strVal1);
      case ClassWriter.NAME_TYPE:
        return i.strVal1.equals(strVal1) && i.strVal2.equals(strVal2);
      case ClassWriter.INDY: {
        return i.longVal == longVal && i.strVal1.equals(strVal1) && i.strVal2.equals(strVal2);
      }
      // case ClassWriter.FIELD:
      // case ClassWriter.METH:
      // case ClassWriter.IMETH:
      // case ClassWriter.HANDLE_BASE + 1..9
      default:
        return i.strVal1.equals(strVal1) && i.strVal2.equals(strVal2) && i.strVal3.equals(strVal3);
    }
  }

}